Injection apparatus for a die casting machine

Abstract

Operation can be switched from low- or high-speed injection process to intensified-pressure injection process by using only one accumulator, and an injection cylinder is composed of a single-acting cylinder, so that the space can be saved, and intensified-pressure surge can be reduced. A coaxial small-diameter portion is formed on the pressure surface side of a piston of the accumulator, a hydraulic oil discharge passage having an inside diameter corresponding to the outside diameter of the small-diameter portion is provided coaxial with the piston, and a passage is provided for guiding intensified-pressure oil in a cylinder chamber of the accumulator.

What is claimed is: 
     
       1. An injection apparatus for a die casting machine, comprising: an injection cylinder for injecting a molten metal in a die cavity and operated by hydraulic oil;   a hydraulic circuit for controlling injection operation of the injection cylinder for low-speed injection, high-speed injection, and intensified-pressure operation such that the casting pressure is increased after a cavity is loaded with a molten metal; and   a piston-type accumulator for accumulating hydraulic oil to be fed into the injection cylinder through said hydraulic circuit,   said accumulator including:   a piston having a pressure surface;   a small-diameter portion coaxially formed on the pressure surface side of the piston;   a hydraulic oil discharge passage having an inside diameter corresponding to the outside diameter of the small-diameter portion and coaxial with the piston; and   a passage for guiding intensified-pressure oil in a cylinder chamber of the accumulator, such that the pressure thereof is intensified by utilizing the ratio between the pressure area of the piston and the area of the small-diameter portion, whereby the oil is delivered to an intensified-pressure oil circuit through the guide passage.   
     
     
       2. The injection apparatus for a die casting machine according to claim 1, which further comprises position detecting means for detecting the position of the piston and arranged at a rod side thereof, and wherein loading the accumulator with the hydraulic oil is controlled in accordance with the piston position. 
     
     
       3. The injection apparatus for a die casting machine according to claim 1, wherein hydraulic oil accumulated in the accumulator is fed into said injection cylinder through a line, and the line is provided with low- and high-speed pilot check valves arranged in parallel with each other, whereby the injection speed is switched between low and high levels.